staging: rtl8192u: Fix static decleration sparse warning.

The function 'ieee80211_check_auth_response' is used only in this
file, so make it static. This patch fixes the following sparse
warning.

'ieee80211_check_auth_response' was not declared. Should it be static?

Signed-off-by: Cihangir Akturk <cakturk@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c

@@ -1921,7 +1921,7 @@ static void ieee80211_process_action(struct ieee80211_device *ieee,
 
 }
 
-void ieee80211_check_auth_response(struct ieee80211_device *ieee,
+static void ieee80211_check_auth_response(struct ieee80211_device *ieee,
 					  struct sk_buff *skb)
 {
 	/* default support N mode, disable halfNmode */